package main
import "fmt"

const PI float64 = 3.1415926

func redius(redis float64) float64{
	var redius = PI * redis * redis
	return redius
}

func main() {
	fmt.Println(PI)
	var banjing = 5.0
	var mianji = redius(banjing)
	fmt.Println("半径是：",banjing, "， 面积是：", mianji)
}